Procatalyst component based on a transition metal compound on a

Details Procatalyst component based on a transition metal compound on a Procatalyst component based on a transition metal compound on a

1994-06-01

1997-09-02

Delmendo, Romulo H.

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

526113, 5261249, 5261253, 5261256, 526351, 502107, 502111, 502113, 502169, C08F 4646

Patent

active

056632487

DESCRIPTION:

BRIEF SUMMARY
The invention relates to an olefin polymerization catalyst the procatalyst component of which comprises a transition-metal compound on a support material of magnesium chloride. The invention also relates to a method for preparing a procatalyst component for an olefin polymerization catalyst of the said type, wherein is melted, produce support material particles, and transition-metal compound. catalyst of the said type for the preparation of polypropylene, and preferably a polypropylene with a broad molecular weight distribution.
.alpha.-olefins are often polymerized using a Ziegler-Natta catalyst system made up of a so-called procatalyst and a cocatalyst. Of these, the procatalyst component is based on a compound of a transition metal belonging to any of Groups IVA-VIII in the Periodic Table of the Elements, and the cocatalyst component is based on an organometallic compound of a metal belonging to any of Groups IA-IIIA in the Periodic Table of the Elements (the groups are defined according to Hubbard, i.e. IUPAC). The catalyst system may also include a support material on which the transition-metal compound is deposited and an internal electron donor which enhances and modifies the catalytic properties and is deposited on the support material together with the transition-metal compound. In addition, a separate so-called external electron donor can also be used together with the procatalyst and the cocatalyst.
The Ziegler-Natta catalysts used for polypropylene polymerization usually produce a polymer having a narrow molecular weight distribution. This material is very suitable for injection molding purposes. However, there are several uses in which a broad molecular weight distribution is required. Especially if a higher melt strength is desired, a wider range of polymer chain lengths would be an advantage. If it is assumed that polymerization takes place at specific so-called active sites in the catalyst, active sites of the same type will produce a polymer material of the same type, in which case the uniformity is seen as a narrow molecular weight distribution. Since a broader molecular weight distribution is required for a number of uses of polypropylene, efforts have been made to prepare catalysts with active sites of a variety of types.
JP application publication 79037911 describes the preparation of a polyolefin having a wide molecular weight distribution by using an active and new procatalyst which is made up of a titanium and/or vanadium compound on a support material. The first component is obtained by treating aluminum oxide with sulfur dioxide, and the other component contains a magnesium halide, a manganese halide, and an organic compound of a metal such as aluminum or zinc, e.g. MgCl.sub.2 MnCl.sub.2 --Al(OR.sub.3).
By this known method it has been possible, for example, to improve the casting properties of the polymer, but the process for preparing the catalyst is too complicated and unconventional in order to be commercially usable.
The object of the present invention is to provide a catalyst comprising a transition-metal compound on a magnesium chloride support material for producing polyolefins having a broad molecular weight distribution. Another aim is a maximal catalyst activity and a suitable catalyst morphology, which will also be reflected in the morphology of the polymer product. The invention also aims at an improved method for the production of an olefin polymerization catalyst of the said type.
These objects have now been achieved with a new olefin polymerization catalyst, the procatalyst component of which has been prepared by (a) contacting magnesium chloride and a lower alcohol and melting the mixture, (b) atomizing the molten mixture and solidifying it by cooling to produce support material particles, (c) reacting the support material particles with a transition metal compound, characterized by adding manganese (II) halide at stage (a) at a rate of a minimum of approximately 0.1% and a maximum of approximately 50% of the total molar amount of magnesium chloride and manganese

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